Atherectomy devices and methods

ABSTRACT

The devices and methods generally relate to treatment of occluded body lumens. In particular, the present devices and methods relate to removal of the occluding material from the blood vessels as well as other body lumens. In some variations, the devices comprise a catheter body, a cutter assembly, a drive mechanism, a torque shaft, and a deflecting mechanism. The deflecting mechanism may be slidable within the catheter body to point the cutter assembly toward a side of a body lumen.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/551,203filed 19 Oct. 2006 (now U.S. Pat. No. 8,007,506), which claims thebenefit of provisional application Ser. No. 60/806,417 filed 30 Jun.2006 and which also claims the benefit of provisional application Ser.No. 60/820,475 filed 26 Jul. 2006, the entirety of each of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

The devices and methods described below generally relate to treatment ofoccluded body lumens. In particular, the present devices and methodrelate to removal of the occluding material from the blood vessels aswell as other body lumens.

Atherosclerosis is a progressive disease. In this disease, lesions ofthe arteries are formed by accumulation of plaque and neointimalhyperplasia causing an obstruction of blood flow. Often plaque isfriable and may dislodge naturally or during an endovascular procedure,leading to embolization of a downstream vessel.

Endovascular clearing procedures to reduce or remove the obstructions torestore luminal diameter allows for increased blood flow to normallevels are well known. Removing the plaque has the effect of removingdiseased tissue and helps to reverse the disease. Maintaining luminaldiameter for a period of time (several to many weeks) allows remodelingof the vessel from the previous pathological state to a more normalstate. Finally, it is the goal of an endovascular therapy to preventshort term complications such as embolization or perforation of thevessel and long term complications such as ischemia from thrombosis orrestenosis.

Various treatment modalities may help to accomplish treatment goals. Inatherectomy, plaque is cut away, or excised. Various configurations areused including a rotating cylindrical shaver or a fluted cutter. Thedevices may include shielding by a housing for safety. The devices mayalso remove debris via trapping the debris in the catheter, in adownstream filter, or aspirating the debris. In some cases a burr may beused instead of a cutter, particularly to grind heavily calcifiedlesions into very small particle sizes. Aspiration may also be used witha burr-type atherectomy device.

Balloon angioplasty is another type of endovascular procedure. Balloonangioplasty expands and opens the artery by both displacing the plaqueand compressing it. Balloon angioplasty is known to cause barotrauma tothe vessel from the high pressures required to compress the plaque. Thistrauma leads to an unacceptably high rate of restenosis. Furthermore,this procedure may not be efficient for treatment of plastic-type plaquetissue, where such tissue can spring back to occlude the lumen.

When clearing such obstructions it is desirable to protect the vesselwall or wall of the body lumen being cleared and to debulk substantiallyall of a lesion. In additional cases, the procedure that clearsobstructions may also be coupled with placement of an implant within thelumen. For example, it may be desirable to deploy a stent to maintainpatency of a vessel for a period of time and/or to achieve local drugdelivery by having the stent elute a drug or other bioactive substance.

On their own, stents fail to perform well in the peripheral vasculaturefor a variety of reasons. A stent with the necessary structuralintegrity to supply sufficient radial force to reopen the artery oftendoes not perform well in the harsh mechanical environment of theperipheral vasculature. For example, the peripheral vasculatureencounters a significant amount of compression, torsion, extension, andbending. Such an environment may lead to stent failure (strut cracking,stent crushing, etc.) that eventually compromises the ability of thestent to maintain lumen diameter over the long-term. On the other hand,a stent that is able to withstand the harsh mechanical aspects of theperiphery often will not supply enough radial force to open the vesselsatisfactorily. In many cases, medical practitioners desire the abilityto combine endovascular clearing procedures with stenting.

Accordingly, a need remains for devices that allow for improvedatherectomy devices that clear materials from body lumens (such as bloodvessels) where the device includes features to allow for a safe,efficient and controlled fashion of shaving or grinding material withinthe body lumen.

SUMMARY OF THE INVENTION

Devices and methods described herein provide improved means of clearingobstructions within body lumens, especially the vasculature. Thefeatures of the devices and methods allow for controlled removal ofocclusive materials. In some variations, the methods and devices alsohave features to convey the materials away from the operative sitewithout the need to remove the devices from the body lumen. Additionalaspects include controlled rates of tissue removal as well as othersafety features to prevent accidental cutting of the lumen wall.Although the devices and methods described herein discuss removal ofmaterials from a blood vessel, in certain cases the devices and methodshave applicability in other body lumens as well. It should be noted thatthe variations and features of the devices described below may beincorporated selectively or in combination with a basic deviceconfiguration that includes a flexible body having a cutter head, wherethe cutter head includes a housing and a cutter, where the housing andcutter are able to rotate relative to each other. Variations include acutter that rotates within the housing, a housing that rotates about thecutter, and combinations thereof.

One variation of the device described herein includes a deviceconfigured to remove material from body structures. The device may be avascular device and have the required structure and configuration tonavigate tortuous anatomy. Alternatively, the device may be a cutterthat has features that are desired when used in other parts of theanatomy.

In any case, such a device may include a catheter body having a proximalend and a distal end, a cutter assembly located at the distal end of thecatheter body, the cutter assembly comprising a housing having at leastone opening and a cutter having at least one cutting surface configuredto rotate relative to the housing, where movement between the housingopening and the cutting surface removes material located therebetween, arotating shaft extending through the catheter body and coupled to thecutter, the shaft having a proximal end adapted to couple to a firstrotating mechanism, and a deflecting member extending along the catheterbody, such that movement of the deflecting member causes deflection ofthe cutter assembly relative to an axis of the catheter.

Variations of the deflecting member may include steerable sheathsadapted to deflect in shape. In some variations the steerable sheath mayinclude a deflecting wire extending through a portion of the sheath,such that axial movement of the deflecting wire deflects the sheath. Thedeflecting wire can be affixed to the cutter assembly, to a portion ofthe catheter body that extends out of the deflecting sheath, or to otherparts of the device as needed.

The deflecting member can also include a pre-shaped mandrel, or tubewhere such features are slidable within or relative to the device toproduce movement of the cutting head relative to an axis of the device.The devices described herein may have any number of features that allowfor locking the device after it is articulated. This feature provides aconsistent diameter when sweeping or navigating through the anatomy.

As discussed herein, some variations of the devices have the ability toarticulate. This articulation allows for steering the device to thetarget site as well as creating a sweeping motion of tissue removal.Accordingly, sheath used in the device can be rotatable about thecatheter body, or about an axis of the catheter.

The devices described herein may have a cutter assembly having a portionof its housing having a curved surface and where the opening forms aplane across the curved surface such that as the cutting surface rotatesacross the opening, a portion of the cutting surface extends out of thehousing through the opening. The cutter assembly may also have variousother features as described below that improve the safety of the deviceas it is articulated while cutting. Furthermore the cutter may have anumber of features to impel or drive cut tissue into the cutter assemblyfor eventual removal by one or more conveying members.

As noted, the devices described herein may have one or more conveyingmembers that convey materials and/or fluids through the device. Such afeature is useful to remove cut tissue and debris from the site duringthe procedure. In some variations, the device may include multipleconveyors to deliver fluids and remove debris. However, the devices ofthe present invention may also have containers for use in capturingdebris or other materials generated during the procedure.

Another feature for use with the inventions herein is the use of a burrrotatably coupled to a tip of the device. The burr can be useful toremove tissue that is otherwise not conducive to cutting with the cutterassembly.

In another variation, the invention may comprise a device having astraightening tube, with a straight distal portion, a catheter bodyhaving a proximal end and a distal end, the catheter body having aflexible section located towards the distal end, such that when locatedin the straight distal portion of the straightening tube the flexiblesection is less curved, a cutter assembly located at the distal end ofthe catheter body, the cutter assembly comprising a housing having atleast one opening and a cutter having at least one cutting surfaceconfigured to rotate relative to the housing, where movement between thehousing opening and the cutting surface removes material locatedtherebetween, and a rotating shaft extending through the catheter bodyand coupled to the cutter, the torque shaft having a proximal endadapted to couple to a first rotating mechanism.

In such a case, placement of the straight distal portion over thecatheter allows for manipulation of the degree of curvature of thecatheter. This feature allows for steering of the device.

As described herein, such a device may have the ability to sweep over anarc to deliver a larger cutting diameter than the diameter of the cutterassembly.

The devices described herein may use a guidewire for advancement throughthe body. In such cases the devices will have guide-wire lumens locatedwithin or about the catheter. Alternatively, a guide-wire section may beaffixed to a portion of the device.

Devices of the present invention typically include a torque shaft todeliver rotational movement to components in the cutter assembly.Alternatively, a torque shaft or other such assembly may be used toproduce the sweeping action described herein. In any case, the torqueshaft may include one or more lumens. Alternatively, the torque shaftmay be a solid or hollow member. Variations of the torque shaft alsoinclude those aspects known in catheter-type devices such ascounter-wound coils, stiffening members, etc. In some variations, thetorque shaft may have the conveying member integrally formed about theexterior or an interior surface of the shaft. Alternatively, or incombination, the conveying member may be placed on (or within) thetorque shaft as described herein.

The invention also includes various methods of debulking material withinbody structures. These structures include occluded blood vessels(whether partially or totally occluded), various organs, cavities withinthe body, or other body lumens.

In one variation a method includes inserting a catheter body having acutter assembly within the blood vessel, rotating the cutter assembly toremove the material and form a first opening in the body lumen,deflecting the first cutter assembly relative to an axis of the catheterbody, rotating the catheter body while rotating the cutter assembly toform a second opening in the body lumen where the second is larger thanthe first opening.

The methods may include the use of any of the devices or features of thedevices described herein. In one variation, the methods includecirculating fluid for contrast to better visualize the obstruction.

As noted herein, combinations of aspects of the devices, systems, andmethods described herein may be combined as needed. Furthermore,combinations of the devices, systems and methods themselves are withinthe scope of the disclosure.

DESCRIPTION OF THE DRAWING FIGURES

FIG. 1A illustrates an exemplary variation of a device according to thepresent invention;

FIG. 1B shows an exploded view of the device of FIG. 1A;

FIG. 1C shows a cross sectional view of the cutting assembly;

FIG. 2A shows alignment of the cutting edges with openings of a housing;

FIG. 2B shows a side view of the cutting assembly demonstrating thesecant effect;

FIG. 2C illustrates a positive rake angle;

FIG. 3 shows a partial cross sectional view of a variation of a torqueshaft having counter wound coils;

FIG. 4A shows a variation of a device configured for rapid exchange;

FIG. 4B illustrates an example of centering a tip of a cutting assemblyover a guide wire;

FIG. 5A shows a conveyor within the device;

FIG. 5B shows a second conveyor within a torque shaft;

FIG. 6A illustrates articulation of a tip of the device;

FIG. 6B-6D shows sweeping of the cutting assembly;

FIG. 6E illustrates another variation where the catheter body includes aset curve in an area that is adjacent to the cutting assembly;

FIG. 7 shows placement of housing windows to prevent damage to thevessel walls;

FIGS. 8A-8I show variations of the device for articulating the cuttinghead;

FIG. 9 shows a device with a burr tip;

FIGS. 10A-10C provide examples of fluid delivery systems;

FIG. 11 shows the device placed within a stent or coil;

FIGS. 12A-12I show variations of devices; and

FIGS. 13A-13C show a system for visualizing and crossing totalocclusions.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1A illustrates an exemplary variation of a device 100 according tothe present invention. As shown the device 100 includes a cutterassembly 102 affixed to a catheter body 120. As shown, the catheter bodymay be optionally located within an outer sheath 122.

FIG. 1B illustrates an exploded view of the device 100 of FIG. 1A. Asshown, the cutter assembly 102 includes a housing 104 with a pluralityof openings 106. A cutter 108 is located within the housing 104. Thecutter 108 includes one or more flutes 110 each of which includes anedge or cutting surface 112. The cutter is coupled to a rotatingmechanism 150. In this variation the rotating mechanism couples to thecutter via a torque shaft 114 that transmits rotational energy from therotating mechanism 150 (e.g., an electric, pneumatic, fluid, gas, orother motor) to the cutter 108. Variations of the devices include use ofa rotating mechanism 150 located entirely within the body of the device100. In one variation, the rotating mechanism 150 may be outside of thesurgical field (i.e., in a non-sterile zone) while a portion of thedevice (e.g., the torque shaft-not shown) extends outside of thesurgical field and couples to the rotating mechanism. FIG. 1B also showsa variation of the device 100 as having a deflecting member 124 (thedeflecting member may be a tendon, wire, tube, mandrel, or other suchstructure). As described in detail below, the devices 100 can havedeflecting members to articulate the cutting head and allow for asweeping motion of cutting.

In another variation, the device 100 may have a catheter body thatcomprises a soft or flexible portion. In one variation, this soft orflexible portion may be on a single side of the device 100 to allowflexure of the device 100 to articulate the cutting head. The flexuremay be obtained with a curved sheath, mandrel, or other means as knownto those skilled in the art.

The device 100 may also include a vacuum source or pump 152 to assist inevacuation of debris created by operation of the device. Any number ofpumps or vacuum sources may be used in combination with the device. Forexample, a peristaltic pump may be used to drive materials from thedevice and into a waste container. FIG. 1B also shows the device 100coupled to a fluid source 154. As with the rotating mechanism, thevacuum source and/or fluid source may be coupled to the device fromoutside the surgical field.

It may be advantageous to rotatably couple the torque shaft to the driveunit electromagnetically, without physical contact. For example, thetorque shaft 114 can have magnetic poles installed at the proximal end,within a tubular structure that is attached to the sheath around thetorque shaft. The stationary portion of the motor can be built into ahandle that surrounds the tubular structure. This allows the continuousaspiration through the sheath without the use of high speed rotatingseals.

As shown in FIG. 1C, in certain variations, the housing 104 can have adistal nose with a center lumen 142 for receiving a mating piece 140 ofthe cutter 108. Such features assists in centering the cutter 104concentrically inside the housing 104. The housing is preferably made ofa strong, wear resistant material such as hardened steels, cobaltchromium, carbides or titanium alloys with or without wear resistantcoatings like TiNi. In particular the use of coatings will allow the useof tool steels which, unless coated, do not have acceptable corrosionresistance and biocompatibility. As noted below, variations of thedevices include the addition of a burr element (as shown below) forgrinding hard tissue such as calcified plaque.

The geometry of the cutter 108 and housing 104 can be used to tailor thedesired degree of cutting. The housing 104 and orientation of theopenings 106 can be used to limit the depth of cutting by the cutter108. In addition, the distal end of the housing 104 may be domed shapedwhile the proximal end may have a cylindrical or other shape. Forexample, by creating larger windows 106 in the housing a larger portionof cutter 108 may be exposed and the rate of cutting increased (for agiven rotation speed). By placing the cutting window 106 on a convexportion of the housing, the debulking effectiveness is much lesssensitive to the alignment of the cutter housing to the lesion, than ifthe window were on the cylindrical portion of the housing. This is a keyperformance limitation of traditional directional atherectomy catheters.In addition, placement of the window on the convex portion of thehousing creates a secant effect (as described below).

FIG. 2A illustrates an additional variation of the device 100 where theopenings 106 may be helical slots that may or may not be aligned withthe cutting surfaces 112 of the cutter 108. For aggressive cutting, theslots 106 and cutting edges 112 are aligned to maximize exposure of thetissue to cutting edges. In other words, the cutting edges 112 andopenings 106 are in alignment so all cutting edges 112 are exposed atthe same time to allow simultaneous cutting. Alternatively, alignment ofthe openings and edges 112 may be configured so that fewer than all thecutting edges 112 are exposed at the same time. For example, thealignment may be such that when one cutting edge 112 is exposed by anopening 106, the remaining cutting edges 112 are shielded within thehousing 104. Variations of such a configuration allow for any number ofcutting edges to be exposed at any given time.

However, to even out the torque profile of the device when cutting, thecutter 108 is configured such that the number edges/cutting surfaces 112of the flutes 110 that are aligned with the housing openings 106 doesnot vary throughout the rotational cycle. This prevents the catheterfrom being overloaded with torque spikes and cyclic torque variationsdue to multiple cutting edges/flutes engaging with tissue in synchrony.In other words, the length of the cutting surface 112 exposed throughthe openings 106 of the housing 104 remains the same or constant.

In the variation shown in FIG. 2B, the cutting surface 112 is configuredto capture debris as it cuts. Typically, the device 100 may be designedwith a secant effect. This effect allows for a positive tissueengagement by the cutter. As the cutter rotates through the opening, thecutting edge moves through an arc, where at the peak of the arc thecutting edge slightly protrudes above a plane of the opening. The amountof positive tissue engagement can be controlled through selection of theprotrusion distance through appropriate design of the housing geometry(for example, by a combination of location and size of the window andradius of curvature of the housing). As shown, the cutting surface 112extends out of the housing 104 through the window 106 as it rotates.This structure can also be designed to drive or impel the debris to theconveying member 118. In this case, the flutes 110 within the cutter 108are helically slotted to remain in fluid communication with theconveying member 118. Variations of the device 100 can also include avacuum source 152 fluidly coupled to the conveying member 118. In orderto improve the impelling force generated by the cutters, variations ofthe cutter have helical flutes 110 and sharp cutting edges 112 that areparallel to each other and are wound from proximal to distal in the samesense as the rotation of the cutter. When the cutter rotates, it becomesan impeller causing tissue debris to move proximally for evacuation.

As shown in FIG. 2C, variations of the device may have cutting surfaces112 with positive rake angles α—that is the cutting edge is pointed inthe same direction as that of the cutter rotation. This configurationmaximizes the effectiveness of the impelling and cutting action (bybiting into tissue and avoiding tissue deflection). The cutter ispreferably made of hard, wear-resistant material such as hardened toolor stainless steels, Tungsten carbide, cobalt chromium, or titaniumalloys with or without wear resistant coatings as described above.However, any material commonly used for similar surgical applicationsmay be employed for the cutter. The outer surfaces of the proximal endof the cutter 108 is typically blunt and is designed to bear against thehousing 104. Typically, these surfaces should be parallel to the innersurface of the housing.

FIGS. 2A-2B also show a surface of the cutter 108 having a curved-inprofile distally and is close to the housing 104 surface. Note thathousing slots 106 with this curved profile allows the cutting edge 112to protrude beyond the housing's outer surface. In other words, theopenings 106 form a secant on the curved surface of the housing 104.Such a feature allows improved cutting of harder/stiffer material likecalcified or stiff fibrous tissue where such tissue does not protrudeinto the housing 104.

By controlling the number of cutting edges 112 that are exposed throughopenings 106 in the housing 104, it is possible to control the relativeamount of cutting engagement (both length of cutting and depth of cut,together which control the volume of tissue removed per unit rotation ofthe cutter). These features allow independent control of the maximumtorque load imposed on the device 100. By carefully selecting thegeometry of the flutes and or cutting edges 112 relative to the openings106 in the housing, it is possible to further control the balance oftorque. For example, the torque load imposed on the device is caused bythe shearing of tissue when the cutter edge passes the rotationallydistal edge of the window. If all cutter edges simultaneously shear, asfor example when the number of housing windows is an even multiple ofcutter edges, the torque varies cyclically with rotation of the cutter.By adjusting the number of cutters and windows so one is not an evenmultiple of the other (for example, by using 5 windows on the housingand 4 cutting edges on the cutter), it is possible to have a moreuniform torque (tissue removal from shearing action) during each cycleof the cutter.

FIG. 3 shows a partial sectional view of a torque shaft 114 that is aset of counter-wound coils, with the outer coil wound at the proper(greater) pitch to form the conveying member 118. Winding the coilscounter to each other automatically reinforces the torque shaft 114during rotation. Alternatively, the torque shaft 114 may be made out ofa rigid plastic, rendered flexible by incorporation of a conveyingmember 118. Although the shaft may be fabricated from any standardmaterial, variations of the shaft include a metal braid embedded inpolymer (PEBAX, polyurethane, polyethylene, fluoropolymers, parylene) orone or more metal coils embedded in a polymer such as PEBAX,polyurethane, polyethylene, fluoropolymers or parylene. Theseconstructions maximize torsional strength and stiffness, as well ascolumn strength for “pushability”, and minimize bending stiffness forflexibility. Such features are important for navigation of the catheterthrough tortuous vessels. In the multi-coil construction, the inner coilshould be wound in the same sense as that of the rotation so that itwould tend to open up under torque resistance. This ensures that theguidewire lumen remain patent during rotation. The next coil should bewound opposite the inner to counter the expansion to keep the inner coilfrom binding up against the outer catheter tube.

FIG. 3 also shows a torque shaft 114 having a central lumen 130.Typically the lumen will be used to deliver a guidewire. In such cases,the central lumen may be coated with a lubricious material (such as ahydrophilic coating or Parylene) or made of a lubricious material suchas PTFE to avoid binding with the guidewire. However, in some variationsa guidewire section is affixed to a distal end of the housing. Moreover,the central lumen of the torque shaft 114 may also be used to deliverfluids to the operative site simultaneously with the guidewire or inplace of the guidewire.

FIG. 4A illustrates a variation of a device 100 configured for rapidexchange. As shown, the device 100 includes a short passage, lumen, orother track 136 for the purpose of advancing the device 100 over aguidewire 128. However, the track 136 does not extend along the entirelength of the device 100. Moreover, an additional portion of the track136 may be located at a distal end of the catheter to center a guidewire128.

This feature permits decoupling of the device 100 and guidewire 128 bymerely pulling the guidewire 128 out of the track 136 (as opposed toneeding to remove the guidewire 128 from the length of the device 136).One benefit of such a feature is that the guidewire 128 may remain closeto the site while being decoupled from the device 100. Accordingly, thesurgeon can advance additional devices over the guidewire and to thesite in a rapid fashion. This configuration allows for quick separationof the catheter from the wire and introduction of another catheter overthe wire since most of the wire is outside of the catheter.

As shown in FIG. 4B, centering the tip of the cutting assembly 102 overa guide wire 128 improves the control, access and positioning of thecutting assembly 102 relative to a body lumen or vessel 2. To accomplishthis, the cutting assembly 102 can have a central lumen to accommodate aguide wire 128. Variations of the device 100 includes a central guidewire lumen runs the length of the catheter through all centralcomponents including the torque shaft and the cutter. As noted above, aguidewire 128 can be affixed to the housing 104 or other non-rotationalcomponent of the cutting assembly 102. In such a case, the guidewire 128may preferably be a short segment that assists with navigation of thedevice through an occluded portion of a body lumen. However, the devices100 can also operate without a guidewire since the head is steerablelike a guidewire.

FIG. 5A illustrates a partial cross-sectional view of the device 100. Asshown, this variation of the device 100 includes a conveyor member 118located within the device 100. The conveyor member 118 may be an augertype system or an Archimedes-type screw that conveys the debris andmaterial generated during the procedure away from the operative site. Inany case, the conveying member 118 will have a raised surface or bladethat drives materials in a proximal direction away from the operativesite. Such materials may be conveyed to a receptacle outside of the bodyor such materials may be stored within the device 100. In one variation,the torque shaft 114 and conveying member 118 extend along the length ofthe catheter.

In some variations, the conveying member 118 may be integral to theshaft 114 (such as by cutting the conveying member 118 into the torqueshaft 114 or by extruding the torque shaft 114 directly with a helicalgroove or protrusion. In an additional variation as shown in FIG. 5B, anadditional conveying member 118 may be incorporated on an inside of thetorque shaft, where the internal conveying member is wound opposite tothat of the external conveying member 118. Such a configuration allowsfor aspiration and debris (via the external conveying member 118) andinfusion (via the internal conveying member 118). Such a dual action canenhance the ability to excise and aspirate plaque by: (1) thinning theblood, whether by viscosity alone or with the addition ofanti-coagulants such as heparin or warfarin (cumadin), (2) improving thepumpability (aspirability) of the excised plaque by converting it into asolid-liquid slurry that exhibits greater pumping efficiency, and (3)establishing a flow-controlled secondary method of trapping emboli thatare not sheared directly into the housing, by establishing a localrecirculation zone.

As noted above, the conveying member 118 can be wound in the samedirectional sense as the cutter 108 and in the same direction ofrotation to effect aspiration of tissue debris. The impeller action ofthe cutter 108 moves the tissue debris from inside the housing 104openings 106 into the torque shaft. The pitch of the cutting edges 112may be matched in to that of the conveying member 118 to furtheroptimize aspiration. Alternatively, the pitch of the conveying member118 may be changed to increase the speed at which material moves once itenters the conveying member 118. As discussed herein, debris can beevacuated outside the body by the conveying member 118 action along thelength of the catheter and with or without supplement of the vacuum 152pump connected to the catheter handle. Alternatively, the debris may beaccumulated in a reservoir within the device.

The device may also include a ferrule 116, as shown in FIG. 1B, thatpermits coupling of the catheter body 120 to the cutter assembly 102.The ferrule 116 may serve as a bearing surface for rotation of thecutter 108 within the cutter assembly 102. In the illustrated variation,the torque shaft 114 rotates inside the outer catheter body 120 andferrule 116 to rotate the cutter and pull or aspirate tissue debris in aproximal direction. The clearance between the catheter tube andconveying member 118, as well as the pitch and thread depth of theconveying member 118, are chosen to provide the desired pumpingeffectiveness.

In one variation of the device, the housing 104 is connected to thecatheter body 120 via the ferrule 116 and thus is static. The cutter 108rotates relative to the housing 104 so the cutting surface 112 on thecutter 108 cooperates with openings 106 on the housing 104 to shear orcleave tissue and trap the tissue inside the housing so that it can beevacuated in a proximal direction using the impeller action of thehelical flutes and vacuum from the torque shaft.

The ferrule 116 can have a distal bearing surface to bear against theproximal surface of the cutter 108 and keeps the cutter axially stablein the housing 104. It can be rigidly bonded/linked to the housing 104using solder, brazing, welding, adhesives (epoxy), swaging, crimped,press-fit, screwed on, snap-locked or otherwise affixed. As shown, theferrule 116 can have holes or other rough features that allow forjoining with the catheter body. While adhesives and heat fusing may beemployed in the construction, such features are not required. Oftenadhesives are unreliable for a small surface contact and heat fusing cancause the tube to degrade. The use of a mechanical locking ring 126allows the cutting assembly 102 to be short. Such a feature is importantfor maximizing the flexibility of the distal section of the catheter asit is required to navigate tortuosity in blood vessels.

In another aspect of the invention, devices 100 can be adapted to steerto remove materials that are located towards a side of the body passage.Such devices may include a deflecting member that permits adjusting theorientation or offset of the cutter assembly 102 relative to a centralaxis of the device. In FIG. 1B, the deflecting member comprises a sheath122 with a deflecting member 132 (such as a tendon, wire, tube, mandrel,or other such structure). However, as described herein, other variationsare within the scope of the device.

FIG. 6A illustrates an example of a variation of a device 100 equippedto have an articulating or steerable cutter assembly 102. The ability tosteer the tip of the device 100 is useful under a number of conditions.For example, when debulking an eccentric lesion as shown, the cuttingassembly 102 should be pointed towards the side of the vessel 2 havingthe greater amount of stenotic material 4. Naturally, this orientationhelps prevent cutting into the bare wall/vessel 2 and focuses thecutting on stenotic tissue 4. As shown in when in a curved section ofthe vessel 2, without the ability to steer, the cutting assembly 102would tend to bias towards the outside of the curve. Steering allows thecutting assembly 102 to point inward to avoid accidental cutting ofvessel wall 2.

The ability to steer the device 100 also allows for a sweeping motionwhen cutting occlusive material. FIG. 6B shows the rotation of thecutting assembly 102. As shown in FIG. 6C, when the cutting assembly 102articulates, rotation of the cutting assembly 102 creates a sweepingmotion. FIG. 6D shows a front view taken along an axis of the vessel toillustrate the sweeping motion causing the cutting assembly 102 to“sweep” over a larger region than the diameter of the cutting assembly.In most cases, when articulated, the device will be rotated to sweepover an arc or even a full circle. The rotation of the cutter may or maynot be independent of the rotation of the device. A user of the devicemay couple the sweeping motion of the cutting assembly with axialtranslation of the catheter for efficient creation of a larger diameteropening over a length of the occluded vessel. The combination ofmovement can be performed when the device is placed over a guidewire,for example by the use of a lead screw in the proximal handle assemblyof the device. In another aspect of the devices described herein, theangle of articulation may be fixed so that the device sweeps in auniform manner when rotated.

A number of variations to control the deflection of the device 100 aredescribed herein. For example, as shown in FIG. 6 the sheath 122 itselfmay have a pre-set curve. In such a case, the area of the catheter body120 adjacent to the cutting assembly 102 will be sufficiently flexibleso as to assume the shape of the curved sheath 122.

FIG. 6E illustrates another variation where the catheter body 120includes a set curve in an area that is adjacent to the cutting assembly102. In this case, the outer sheath 122 can be made to be straightrelative to the catheter body 120. Accordingly, advancement of thecurved portion of the catheter body 120 out of the sheath 122 causes thecatheter body 120 to assume its curved shape. The degree of articulationin such a case may be related to the degree of which the catheter body120 is advanced out of the sheath 122.

In addition, the shape of the housing 104 as well as the location of thewindows 106 can be chosen so that when the device 100 is substantiallyaligned with the lesion, or engages it at less than some critical attackangle, it will cut effectively. However, when pivoted at an anglegreater than the critical angle, the cutting edges or grinding elementwill not engage the lesion as shown in FIG. 7. This means that at largedeflections, as the catheter tip approaches the vessel wall, itautomatically reduces its depth of cut and ultimately will not cut whenthe critical angle is exceeded. For example, the cutter distal tip isblunt and does not cut. As the catheter tip is deflected outward, theblunt tip contacts the vessel and keeps the cutting edges proximal tothe tip from contacting the vessel wall. Also the wire in combinationwith the device can also act as a buffer to prevent the cutting edgesfrom reaching the vessel.

As mentioned above, variations of the device 100 allow directionalcontrol of the cutting assembly 102. In those variations where aslidable, torqueable sheath advances relative to the catheter body 122(either external or internal to the catheter body) that can be flexed atthe distal end. With the sheath flexed the catheter tip is pointed inthe direction of the flex and the degree of bias is affected by theamount of flex on the sheath. The sheath can be rotated about thecatheter or vessel long axis to change the direction of the cuttingassembly. Also as noted above, this rotation can also effect a sweep ofthe cutting assembly 102 in an arc or a circle larger than a diameter ofthe cutter 102 (e.g. see FIG. 6D). Such a feature eliminates the need toexchange the device for a separate cutting instrument having a largercutting head. Not only does such a feature save procedure time, but thedevice is able to create variable sized openings in body lumens.

As shown in FIG. 8A, the tension on a slidable wire 132 in the wall ofthe sheath 122 can cause flexure of the sheath 122. Compression of thewire can also cause flexure of the sheath in the opposite direction. Inone variation, the sheath 122 can be attached to the housing 104 of thecutting assembly 102. Since the housing 104 is rotatable relative to thecutter 108 and the torque shaft 114, the sheath 122 can rotateindependently of the torque shaft 114 and cutter 108 to either sweep thecutting assembly 102 or to change direction of the articulated cuttingassembly 102 at an independent rate.

In another variation of the device 100, as shown in FIG. 8B, a preshapedcurved wire or mandrel 134 can be advanced in a lumen in either thesheath 122 or catheter 120. As the mandrel 134 advances, the devicetakes the shape as shown in FIG. 8C. FIGS. 8D-8I illustrate additionalmechanisms for flexing the device 100. Such mechanisms can include sideballoons 160, meshes, wire loops 164, coils 166, and arms or mandrels168 and other such structures. These features can be incorporated intocatheter body 120 itself or into the sheath 122. If located in thecatheter body 122, the entire catheter can be rotated to steer the tipin different directions. A curved or helical guidewire 170 can also beused to effect the flexion of the catheter tip as shown in FIGS. 8D-8E.The wire can also be actively flexed to control the degree of catheterflexion. All of these deflecting mechanisms can cause the catheter to bedeflected in one plane or it can be deflected in three dimensions. Thecurve on the wire can be in one plane or in 3 dimensions. The sheath canbe flexed in one plane or 3 dimensions. Another way to achieve flexionat the distal tip of the catheter is to only partially jacket the distalend with one or more polymers. A bevel at the distal end and/or varyingcombinations of jacketing and polymers can be used to change theposition of the moment arm. This changes the flexibility of the distalend and allows proper deflection.

In addition to providing a means for deflecting the catheter, andallowing the user to sweep the distal tip to engage the lesion asdesired, it is also possible to link a separate torque control device tomanually or automatically control the sweep of the catheter, independentof the axial control of the catheter insertion and the rotation controlof the cutter within the housing. Automatic control may be performedopen-loop by user entered settings and activating a switch, or withfeedback control designed to further optimize cutting effectiveness,procedural efficiency, and safety. Example structures of how to lock thearticulation of the sheath/catheter into place include a lockablecollar, a stopper, and friction lock detect mechanisms with one or moresprings, coils, or hinges.

Additional components may be incorporated into the devices describedherein. For example, it can be desirable to incorporate transducers intothe distal region of the catheter to characterize the plaque or toassess plaque and wall thickness and vessel diameter for treatmentplanning; also transducers may be desired to indicate the progression ofdebulking or proximity of cutter to vessel wall. For example, pressuresensors mounted on the catheter housing can sense the increase incontact force encountered in the event that the housing is pressedagainst the vessel wall. Temperature sensors can be used to detectvulnerable plaque. Ultrasound transducers can be used to image luminalarea, plaque thickness or volume, and wall thickness. Optical coherencetomography can be used to make plaque and wall thickness measurements.Electrodes can be used for sensing the impedance of contacted tissue,which allows discrimination between types of plaque and also vesselwall. Electrodes can also be used to deliver impulses of energy, forexample to assess innervation, to either stimulate or inactivate smoothmuscle, or to characterize the plaque (composition, thickness, etc.).For example, transient spasm may be introduced to bring the vessel to asmaller diameter easier to debulk, then reversed either electrically orpharmaceutically. Electrical energy may also be delivered to improve thedelivery of drugs or biologic agents, by causing the cell membrane toopen in response to the electric stimulation (electroporation). Onemethod of characterization by electrical measurement is electricalimpedance tomography.

As shown in FIG. 9, a cutter assembly 102 can also have a burrprotruding out its nose. Although the burr 180 may have any type ofabrasive surface, in one variation, this burr is blunt and has fine grit(such as diamond grit) to allow for grinding of heavily calcified tissuewithout injuring adjacent soft tissue. This combination of a burr andcutter allow the distal assembly to remove hard stenotic tissue(calcified plaque) using the burr while the shaving cutter removessofter tissue such as fibrous, fatty tissue, smooth muscleproliferation, or thrombus. In variations, the burr can also havehelical flutes to help with aspiration, or the burr can be incorporatedto a portion of the cutting edge (for example, the most distal aspect ofthe cutter).

Infusing solutions (flush) into the target treatment site may bedesirable. Infused cool saline can prevent heating of blood and othertissue, which reduces the possibility of thrombus or other tissuedamage. Heparinized saline can also prevent thrombus and thin out theblood to help maximize effectiveness of aspiration. The flush can alsoinclude drugs such as Rapamycin, Paclitaxel or otherrestenosis-inhibitors. This may help to prevent restenosis and mayresult in better long term patency. The flush may include paralytics orlong-acting smooth muscle relaxants to prevent acute recoil of thevessel. FIGS. 10A-10C illustrate variations of flushing out the device100. The flush can be infused through the guide wire lumen (FIG. 10A), aside lumen in the catheter shaft (FIG. 10B) or tube, the space betweenthe flexing sheath and the catheter and/or the sideports in theguidewire (FIG. 10C). Flush can come out of a port at the distal end ofthe cutter head pointing the flush proximally to facility aspiration.Alternatively, by instilling the flush out the distal end of the cutterhousing over the rounded surface, the flow may be directed rearward bythe Coanda effect. The restenosis-inhibitors can be carried bymicrocapsules with tissue adhesives or velcro-like features on thesurface to stick to inner vessel surface so that the drug adheres to thetreatment site, and to provide a time-release controlled by theresorption or dissolving of the coating to further improve efficacy.Such velcro-like features may be constructed with nanoscale structuresmade of organic or inorganic materials. Reducing the volume of foreignmatter and exposing remaining tissue and extracellular matrix to drugs,stimulation, or sensors can make any of these techniques more effective.

Another way to infuse fluid is to supply pressurized fluid at theproximal portion of the guidewire lumen (gravity or pressure feed)intravenous bag, for example. A hemostatic seal with a side branch isuseful for this purpose; tuohy-borst adapters are one example of a meansto implement this.

Balancing the relative amount of infusion versus fluid volume aspiratedallows control over the vessel diameter; aspirating more fluid than isinstilled will evacuate the vessel, shrinking its diameter, and allowcutting of lesion at a greater diameter than the atherectomy catheter.This has been a problem for certain open cutter designs that useaspiration, because the aggressive aspiration required to trap theembolic particles evacuates and collapses the artery around the cutterblades; this is both a performance issue because the cutter can bog downfrom too high torque load, and the cutter can easily perforate thevessel. The shielded design described here obviates both problems, andfurther requires less aggressive aspiration to be effective, giving awider range of control to the user.

The devices of the present invention may also be used in conjunctionwith other structures placed in the body lumens. For example, as shownin FIG. 11, one way to protect the vessel and also allow for maximumplaque volume reduction is to deploy a protective structure such as athin expandable coil or an expandable mesh 182 within a lesion. As thisstructure expands after deployment, the thin wire coil or the strutspush radically outward through the plaque until it becomes substantiallyflush with the vessel wall. This expansion of thin members requiresminimal displacement of plaque volume and minimizes barotrauma producedin balloon angioplasty or balloon expanded stent delivery. Once theprotective structure has expanded fully, atherectomy can be performed tocut away the plaque inside to open up the lumen. The vessel wall isprotected by the expanded structure because the structure members (coilor struts) resist cutting by the atherectomy cutter, and are disposed ina way that they cannot invaginate into the cutter housing (and therebybe grabbed by the cutter). It is also possible to adjust the angle ofthe windows on the atherectomy catheter cutter housing so that they donot align with the struts or coils; the adjustment to orientation may beaccounted for in the coil or strut design, in the cutter housing design,or both. Furthermore, the protective member can be relatively flexibleand have a low profile (thin elements), so that it may be left in placeas a stent. Because the stent in this case relies mainly uponatherectomy to restore lumen patency, it may be designed to exert farless radial force as it is deployed. This allows usage of greater rangeof materials, some of which may not have as high of stiffness andstrength such as bioresorpable polymers. Also, this allows a moreresilient design, amenable to the mechanical forces in the peripheralarteries. It also minimizes flow disruption, and may be designed tooptimize flow swirl, to minimize hemodynamic complications such asthrombosis related to the relatively low flows found in the periphery.It is also possible to perform atherectomy prior to placing theprotective structure, whether or not atherectomy is performed afterplacing the structure.

Additional Variations of systems include devices 100 having a cuttingassembly 170 comprising spinning turbine-like coring cutter 172 as shownin FIG. 12A. FIG. 12B shows a side view of the coring cutter 170. Inuse, the coring cutter can be hydraulically pushed to drive the sharpedge through tissue. The turbine like cutters has helical blades 174 onthe inside of the sharp cylinder housing 176 (shell). The coring cutter170 may also have spokes or centering devices 184 as shown to center theshell about the guidewire. This helps to keep the cut of the plaquecentered about the vessel wall for safety. The spokes also act as animpeller to pull stenotic tissue back and this helps to drive the cutterforward as well as achieve aspiration to minimize embolization. In thehydraulically driven cutter design, an anchor 186 is deployed in tissueand is connected to a backstop 192. A balloon or hydraulic chamber 188is then pressurized to expand and pushes the cutting blade 190 forwardthrough the lesion (See FIG. 121). One advantage of this approach may bethat the technique is similar to angioplasty (which involves pumping upa balloon with an endoflator). One means of anchoring is to use ananchoring guidewire, for example, a guidewire with an inflatable balloonto be placed distal to the atherectomy catheter. Alternatively, thetechnique of anchoring distally can be used with the previouslydescribed torque shaft driven atherectomy catheter.

It is also possible to use the devices and methods described here torestore patency to arterial lesions in the coronary circulation and inthe carotid circulation, both by debulking de novo lesions and bydebulking in stent restenosis.

The devices and methods described herein also work particularly well inlesions that are challenging to treat with other methods: atbifurcations, in tortuous arteries, and in arteries which are subject tobiomechanical stresses (such as in the knee or other joints).

In a further variation of the devices described here, the motor driveunit may be powered by a controller that varies the speed and torquesupplied to the catheter to optimize cutting efficiency or toautomatically orbit the cutter using variable speed with a fixedflexible distal length of catheter (or providing further orbitingcontrol by controlling the length of the distal flexible section of thecatheter).

It is also possible to use feedback control to operate the catheter in avessel safe mode, so that the rate of cutting is decreased as the vesselwall is approached. This may be accomplished through speed control, orby reducing the degree to which the cutting blades penetrate above thehousing window by retracting the cutter axially within the housing.Feedback variables could be by optical (infrared) or ultrasoundtransducer, or by other transducers (pressure, electrical impedance,etc.), or by monitoring motor performance. Feedback variables may alsobe used in safety algorithms to stop the cutter, for example in a torqueoverload situation.

The atherectomy catheter may be further configured with a balloonproximal to the cutter, for adjunctive angioplasty or stent delivery.The catheter may optionally be configured to deliver self-expandingstents. This provides convenience to the user and greater assurance ofadjunctive therapy at the intended location where atherectomy wasperformed.

Further methods include use of similar devices to debulk stenosis in AVhemodialysis access sites (fistulae and synthetic grafts), as well as toremove thrombus. By removing the cutter housing and recessing the flutedcutter within the catheter sheath, a suitable non-cutting thrombectomycatheter may be constructed.

Other methods of use include excising bone, cartilage, connectivetissue, or muscle during minimally invasive surgical procedures. Forexample, a catheter that includes cutting and burr elements may be usedto gain access to the spine for performing laminectomy or facetectomyprocedures to alleviate spinal stenosis. For this application, thecatheter may be further designed to deploy through a rigid cannula overpart of its length, or have a rigid portion itself, to aid in surgicalinsertion and navigation.

For this reason, it is advantageous to couple atherectomy with stenting.By removing material, debulking the lesion, a lesser radial force isrequired to further open the artery and maintain lumen diameter. Theamount of debulking can be tuned to perform well in concert with themechanical characteristics of the selected stent. For stents that supplygreater expansion and radial force, relatively less atherectomy isrequired for satisfactory result. An alternative treatment approach isto debulk the lesion substantially, which will allow placement of astent optimized for the mechanical conditions inherent in the peripheralanatomy. In essence, the stent can support itself against the vesselwall and supply mild radial force to preserve luminal patency. The stentmay be bioresorbable, and/or drug eluting, with the resorption orelution happening over a period for days to up to 12 weeks or more. Aperiod of 4 to 12 weeks matches well with the time course of remodelingand return to stability as seen in the classic wound healing response,and in particular the known remodeling time course of arteries followingstent procedures. In addition, the stent geometry can be optimized tominimize thrombosis by inducing swirl in the blood flow. This has theeffect of minimizing or eliminating stagnant or recirculating flow thatleads to thrombus formation. Spiral construction of at least theproximal (upstream) portion of the stent will achieve this. It is alsobeneficial to ensure that flow immediately distal to the stent does notcreate any stagnant or recirculation zones and swirl is a way to preventthis also.

FIG. 13 illustrates another variation of a device for clearingobstructions within body lumens. In some cases where a vessel is totallyoccluded, a tough fibrous or calcific cap 6 completely or almostcompletely blocks the lumen. Because of this blockage, fluid cannot flowpast the occlusion. This stagnation also makes it difficult orimpossible to properly insert a wire across the lesion with anatherectomy device or stiff catheter.

In a typical case of a total occlusion, it is also difficult if notimpossible to visualize the lumen near the occlusion because anyinjected contrast agents cannot flow through the occlusion site.

FIG. 13A shows a system for treating total occlusions. The system caninclude a support catheter comprising a support tube or catheter 200,having a central lumen 202, the catheter may include side lumens orports 206, for flush and aspiration. The catheter central lumen 202 canbe used to deliver contrast agents 208. In addition, tip centeringmechanisms, and an atraumatic tip can be useful. The support cathetercan be used with any lumen-creating device 210, such as the devices 100described above, a laser catheter, an RF probe, or an RF guidewire. Whenusing a coring cutter as shown in FIG. 13, the cutter can have a sharpedge at its tip, helical flutes, helical grooves, or any other mechanismthat enables penetration of the fibrous or calcific cap. The cutter andthe shaft can be advanced forward within the support catheter, and oneor more balloons or baskets can also be deployed by the support catheterto help center it in the vessel.

The lumen-creating device 200 can optionally be made to have a shoulder212 at its distal end, as shown in FIG. 13A. The shoulder 212 acts as astop to limit the depth at which the device 200 protrudes beyond thesupport catheter 200. Such a safety measure may be desired to protectthe vessel wall. Driving the device 200 through the tough fibrous capcreates a lumen in the cap. A guidewire may then be placed into thelumen created in the fibrous cap. The coring cutter may be removed withthe core.

Next, a guidewire can be used with a cutter assembly to remove some orall of the remaining mass in the vessel. Alternatively, the initiallumen made may be adequately large without further atherectomy.Technical success is typically less than 30 percent or less than 20percent residual stenosis. Also, balloon angioplasty with or withoutstenting may be performed following establishment of a guidewire lumenwith a support catheter and a lumen-creating catheter.

Contrast injection and aspiration ports near the distal end of thesupport circulate contrast agents, enabling the use of fluoroscopy tovisualize the lumen adjacent to the total occlusion during diagnosis ortreatment. The central lumen 202 of the support catheter 200 can also beused to inject or aspire the contrast agents 208. The contrast agentscan circulate through the center lumen 202 in the support catheter 200and at least one port 206 in various configurations. The fluid cancirculate about the distal tip of the catheter, the motion of the fluidbeing circular as shown in FIG. 13B. For example, the fluid can beinjected through the central lumen 202, travel around the distal tip,and then is aspirated back into the support catheter through ports 206on the side of the surface of the support catheter 200. To illustrateanother possible configuration, the fluid can be ejected through theside ports, and then aspired through the central lumen. Thisrecirculation of the contrast agent permits imaging of the vessel at thesite of the occlusion.

It is noted that the descriptions above are intended to provideexemplary embodiments of the devices and methods. It is understood that,the invention includes combinations of aspects of embodiments orcombinations of the embodiments themselves. Such variations andcombinations are within the scope of this disclosure.

The invention claimed is:
 1. A vascular device for cutting and removingocclusive material from a body lumen, the device comprising: a catheterbody sized and configured for axial advancement in the body lumen, thecatheter body having a center axis along which axial advancement occursand including spaced apart proximal and distal ends, the distal endbeing sized and configured for rotation about the center axis from theproximal end of the catheter body, a cutter assembly having an outsidediameter attached at the distal end of the catheter body, the cutterassembly comprising a housing having at least one opening and a cutterhaving at least one helical cutting surface configured to rotate aboutthe central axis relative to the housing to cut and convey the occlusivematerial from the body lumen into the housing; a drive mechanism at theproximal end of the catheter body; a torque shaft coupled to the drivemechanism and extending through the catheter body and coupled to thecutter to rotate the helical cutting surface about the center axisrelative to the housing, a deflecting mechanism slidable within thecatheter body in response to a force applied at the proximal end of thecatheter body for deflecting the cutter assembly relative to the centeraxis of the catheter body to point the cutter assembly toward a side ofthe body lumen without necessitating axial advancement of the catheterbody in the body lumen, and a torque control device separate from thedeflecting mechanism to rotate the distal end of the catheter body whilethe cutter assembly is deflected, to sweep the cutter assembly in an arcabout the center axis to cut occlusive material in a region larger thanthe outside diameter of the cutter assembly, wherein the torque controldevice manually or automatically controls the sweep of the cutterassembly.
 2. A device according to claim 1 wherein the torque shaftincludes a lumen extending through the torque shaft accommodatingpassage of a guide wire.
 3. A device according to claim 2 wherein thelumen of the torque shaft extends through the cutter assembly.